The present invention relates generally to magnetic heads and more particularly to a planar magnetoresistive head. There is a constant push to increase the density of recorded information on a magnetic medium. As the density increases, the magnetic head for reading and writing information into the medium has to be scaled down correspondingly. Different methods have been used to scale down the magnetic head. A constant theme is to reduce the size of a head gap but still maintain the signal-to-noise ratio of the head. The head gap is a gap positioned on an air-bearing surface (ABS) above the magnetic medium, for exciting and sensing magnetic transitions in the medium.
One prior art method uses a magnetoresistive element (MRE) with one of its edges at the ABS for sensing the magnetic signals from the magnetic medium. Unfortunately, the configuration exposes the MRE to wear and corrosion. Moreover, the MRE usually exhibits asymmetric cross-track profiles, as described in "Gigabit Density Recording Using Dual-Element MR/Inductive Heads on Thin-Film Disks," written by Tsang et. al. and published in the IEEE Transactions on Magnetics, Volume 26, No. 5, in September 1990. Various attempts have been made to move the MRE away from the ABS and to correct for the asymmetry.
One prior art method moves the MRE away from the ABS by bridging the MRE across the two arms of a magnetic yoke in a dual track head. The magnetic yoke with a write coil is for writing, and the MRE is for reading information. In this method, a thin-film ferromagnetic material is deposited on a substrate as the yoke, and then a thin-film Nan-Yeh type MERE is deposited away from the head gap of the yoke. Since the structure is in thin-films, relatively high reluctance paths are created from the head gap to the MRE. In this method, the yoke has a back gap to decrease the leakage flux in the yoke during the read operation. However, such a structure increases the susceptibility of the head to the stray magnetic flux in the vicinity of the head. To reduce the effect of the stray flux, magnetic shields are added. On the other hand, the shields, due to their proximity to the thin-film yoke and the MRE, increase the leakage flux. Both the high reluctance paths and the shields decrease the reading sensitivity.
Another prior art method scales down the head gap in a silicon planar head and then places an MRE across the gap on the side opposite to the ABS so as to move the MRE away from the ABS. However, as the head gap is decreased in size for high resolution, the leakage flux through the head gap increases significantly. Moreover, stray magnetic flux tends to go through the MRE increasing noise during reading. The increase in the leakage flux and the stray magnetic flux again decreases the reading sensitivity.
It should be apparent from the foregoing that there is still a need for a magnetic head without the aforementioned problems for high density recording.